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Biomedical subjects

G Austin

Publications and source records attributed to G Austin.

64 records · Page 4Linked to original sources
PubMed1966

The kinetics of osmotic transport through pores of molecular dimensions.

This paper presents a theoretical analysis of the kinetics of osmotic transport across a semipermeable membrane. There is a thermodynamic connection between the rate of flow under a hydrostatic pressure difference and the rate of flow due to a difference in solute concentration on the two sides. One might therefore attempt to calculate the osmotic transport coefficient by applying Poiseuille's equation to the flow produced by a difference in hydrostatic pressure. Such a procedure is, however, inappropriate if the pores in the membrane are too small to allow molecules to "overtake." It then becomes necessary to perform a statistical calculation of the transport coefficient, and such a calculation is described in this paper. The resulting expression for the number of solvent molecules passing through a pore per second is J = m D(1) deltan(1)/l(2) where m is the number of solvent molecules in the pore, l is the length of the pore, D(1) is the self-diffusion coefficient of the solute, and deltan(1) the difference in solvent mole fraction on the two sides of the membrane. This equation is used for estimating the number of pores per unit area of the squid axon membrane; the result is 6 x 10(9) pores/cm(2).

Biological Transport↗
PubMedDate not supplied

Cerebral blood flow in patients undergoing microanastomosis for modification for prevention of stroke.

The high incidence of stroke has been considered and the importance of measuring cerebral blood flow (CBF) in patients with transient ischemic attacks has been emphasized. A brief description has been given of the non-invasive method of measuring CBF using a brief bolus injection of 133xenon into any convenient arm vein. The values of CBFg = 75 +/- 8 and CBFw = 24 +/- 2 in ml per 100 g per M compared closely to those obtained by the internal carotid method of measurement. Cerebral blood flow in the gray matter, CBFg is the more sensitive measurement and is used almost exclusively to evaluate patients undergoing microneurosurgical anastomosis for cerebral ischemia in an attempt to prevent or modify stroke. The post operative studies in patients who had a pre operative depression of CBFg greater than 2 S.D. showed improvement in both the frontal and parietal regions. The latter was more significant with p less than 0.04 using paired t-tests.

Carotid Artery, Internal↗
PubMedDate not supplied

The significance of the extracellular matrix in intracranial aneurysms.

To what extent might change sin the extracellular matrix proteins in intracranial aneurysms (IA) or parent artery (PA) wall contribute to enlargement? Using IA specimens obtained from the coroner's office, the wall structure by light (Trichrome and Actin stains) and immunofluorescent microscopy (IF) (collagen I and fibronectin) have been studied in 18 specimens. It is well known that IA only arise when there is a deficiency in the internal elastic membrane and some breakdown in the media. The results show a normal three layer structure of intima, media, (muscularis), and adventitia in the PA extending out into the neck of the aneurysm. Immunofluorescent stains (IS) show collagen I and fibronectin limited to the adventitia and muscularis, respectively, of the PA and control arteries. The enlarging IA wall shows almost complete loss of this architecture. By IF stain, collagen I and fibronectin are intermingled throughout the IA wall. It is postulated that loss of structure and the confining muscularis layer permit easier elastic enlargement from a more or less homogeneous wall structure.

Actins↗